The variable associations between PFASs and biological aging by sex and reproductive stage in NHANES 1999-2018.

BACKGROUND: Per- and polyfluoroalkyl substances (PFASs) are endocrine disrupting chemicals that have myriad effects on human physiology. Estrogenic PFASs may influence biological aging by mimicking the activity of endogenous estrogens, which can decrease inflammation and oxidative stress and enhance telomerase activity. We hypothesized that PFAS exposure would be differentially associated with measures of biological aging based on biological sex and reproductive stage. METHODS: We analyzed associations between serum PFAS levels and measures of biological aging for pre- and postmenopausal women and men (n = 3193) using data from the 2003 to 2018 waves of the National Health and Nutrition Examination Survey. Examining PFASs both individually and in mixture models, we investigated four measures of clinical aging (Homeostatic Dysregulation, the Klemera-Doubal Method, Phenotypic Age Acceleration, and Allostatic Load), oxidative stress, and telomere length. RESULTS: PFOA and PFOS were negatively associated with Phenotypic Age Acceleration (e.g. decelerated aging) for men B = -0.22, 95% CI: -0.32, -0.12; B = -0.04, 95% CI: -0.06, -0.03) , premenopausal women (B = -0.58, 95% CI: -0.83, -0.32; B = -0.15, 95% CI: -0.20, -0.09), and postmenopausal women (B= -0.22, 95% CI: -0.43, -0.01; B = -0.05, 95% CI: -0.08, -0.02). In mixture models, we found net negative effects for Phenotypic Age Acceleration and Allostatic Load for men, premenopausal women, and postmenopausal women. We also found significant mixture effects for the antioxidants bilirubin and albumin among the three sample groups. We found no evidence to support effects on telomere length. DISCUSSION: Our findings suggest that PFAS exposure may be inversely associated with some measures of biological aging at the relatively low levels of exposure in this sample, regardless of reproductive stage and sex, which does not support our hypothesis. This research provides insights into how PFAS exposure may variably influence aging measures depending on the physiological process investigated.

Bicuculline induces free fatty acid release from phospholipids in neuro-2A cells in culture.

This study characterizes free fatty acid release in a neuroblastoma cell line (Neuro-2A), a potential model system for the study of factors that control phospholipase A2 in neurons. Two compounds, bicuculline (an antagonist at gamma-aminobutyric acid receptors), and A23187 (a Ca2+ ionophore), were examined. The release of endogenous fatty acids and the turnover of radiolabeled arachidonic and docosahexaenoic acids were measured. The cells actively incorporated radiolabeled fatty acids into various glycerolipid pools. Both endogenous fatty acids and radiolabeled fatty acids were released from glycerolipids in a time-dependent manner. Phosphatidylcholine was a major source of released fatty acids. Release of free fatty acids was markedly stimulated by both bicuculline and A23187. We conclude that the Neuro-2A cells contain phospholipase activity that is sensitive to Ca2+ ionophore and bicuculline, and may provide a good system for further studies on the regulation of phospholipase A2 in neurons.

Enkephalin degradation in the guinea-pig ileum: effect of aminopeptidase inhibitors, puromycin and bestatin.

Degradation of enkephalin by aminopeptidases has been established as an important functional mechanism that terminates the pharmacological action of enkephalins in the guinea-pig ileum. Aminopeptidases are a family of enzymes and little is known regarding the specificity of individual enzymes with respect to the degradation of enkephalins. Puromycin is a general inhibitor of aminopeptidases and bestatin is a more selective inhibitor of Leu-aminopeptidases and aminopeptidase B. Both agents are capable of inhibiting enkephalin degradation in broken cell preparations from brain. However, only bestatin enhanced the pharmacological response to enkephalin in the guinea-pig ileum and ileal longitudinal muscle. Bestatin enhanced the response to enkephalin in a concentration-dependent fashion. Furthermore, bestatin also decreased the formation of [3H]Tyr and increased [3H]Leu-enkephalin content after incubation of the guinea-pig ileum with [3H]Leu-enkephalin. In contrast, puromycin did not shift the concentration-response curve to Met-enkephalin in either the intact guinea-pig ileum or the ileal longitudinal muscle and, likewise, no alteration in the degradation of [3H]Leu- or Met-enkephalin occurred with puromycin. A small enhancing effect of puromycin on the duration of the inhibitory effect of enkephalin was observed only in the guinea-pig longitudinal muscle. This enhancement cannot be explained by an effect on enkephalin degradation, but may be related to some other action of puromycin. These data support the importance of aminopeptidase activity to the degradation of enkephalin and indicate that enzymes which have properties in common with Leu-aminopeptidases rather than arylamidases may be the primary aminopeptidases responsible for terminating the pharmacological actions of enkephalins in intact guinea-pig ileal preparations.

Analysis of the beta 1 and beta 2 adrenoceptor interactions of the partial agonist, clenbuterol (NAB365), in the rat jugular vein and atria.

The potent bronchodilator, clenbuterol, was compared to other beta adrenoceptor agonists with regard to affinity and efficacy for interaction with beta 1, and beta 2 adrenoceptors in the rat jugular vein and atria. Clenbuterol was a potent partial beta adrenoceptor agonist in both tissues based on the following observations: 1. Maximal relaxation of the jugular vein and increases in atrial rate to clenbuterol were less than maximal responses to other beta adrenoceptor agonists. 2. Clenbuterol antagonized responses to the stronger agonist, isoproterenol, in both tissues and 3. the equilibrium dissociation constant for clenbuterol approximated the ED50 concentration for vascular relaxation and increases in atrial rate, a characteristic of some, but not all, partial agonists. Relative to other beta adrenoceptor agonists, clenbuterol showed high affinity toward both beta 1 and beta 2 adrenoceptors and selectively toward beta 2 adrenoceptors. Equilibrium dissociation constants were 38 and 6.3 nM for beta 1 and beta 2 adrenoceptors, respectively. The high affinity of clenbuterol toward beta 1 and beta 2 adrenoceptors was coupled to a low relative efficacy of clenbuterol to activate either beta 1 or beta 2 adrenoceptors. Most beta 2 adrenoceptor agonists such as isoproterenol or salbutamol require approximately 1-3% adrenoceptor occupation for 40-50% relaxation of the jugular vein whereas clenbuterol required approximately 100% adrenoceptor occupation for a similar response. Thus, based on our analysis, the high agonist potency of clenbuterol results primarily from the high affinity toward beta adrenoceptors rather than efficient activation of the adrenoceptor as occurs with isoproterenol or salbutamol.

In vitro comparison of the pre- and postsynaptic alpha adrenergic receptor blocking properties of prazosin and tiodazosin (BL5111).

Tiodazosin (BL5111) is a structural analogue of prazosin that is currently being evaluated for clinical efficacy in the treatment of hypertension. Like prazosin, tiodazosin was a potent competitive postsynaptic alpha adrenergic receptor antagonist. Although tiodazosin exhibited an affinity for the postsynaptic alpha receptor that was 17 times lower than prazosin, tiodazosin was still 4 times more potent than phentolamine in this regard. Under in vitro conditions, tiodazosin, like prazosin, also produced a noncompetitive antagonism of alpha adrenergic receptors in the portal vein, did not show marked affinity for presynaptic alpha adrenergic receptors, and lacked any measurable direct vasodilator effects (nonreceptor mediated) independent of alpha adrenergic receptor blockade.

In vitro relaxation of arteries and veins by prazosin: alpha-adrenergic blockade with no direct vasodilation.

Controversy exists regarding the mechanism by which prazosin lowers blood pressure without a marked increase in heart rate; a mechanism involving both sympatholytic activity and direct smooth muscle relaxation has been suggested. alpha-Adrenergic receptor blockade by prazosin is well documented and occurred to exogenous norepinephrine and to field stimulation in vitro in rat arteries and veins. A parallel shift of the norepinephrine concentration response curves in the aorta and mesenteric artery contrasted with a nonparallel shift and a marked depression of maximal norepinephrine responses in the inferior vena cava, portal, iliac and femoral veins. Nonspecific direct acting vasodilators will antagonize contractile responses to all agonists. However, prazosin (10(-8) M) specifically antagonized norepinephrine-induced responses. Concentration response curves to potassium chloride or to serotonin were not affected in these rat tissues. In addition, prazosin (up to 10(-6) M) did not significantly relax aortic tissue previously contracted with potassium chloride or serotonin, whereas the vasodilator, nitroglycerin, produced a clear relaxation. Prazosin only reduced the tone of vessels contracted with norepinephrine. These data indicate that prazosin exhibits minimal, if any, direct smooth muscle relaxant properties in concentrations higher than those producing alpha-adrenergic receptor blockade, and relaxes rat veins by a mechanism involving alpha-adrenergic receptor blockade.

Rat jugular vein relaxes to norepinephrine, phenylephrine and histamine.

Circular muscle of the rat external jugular vein contracted to serotonin, angiotensin and potassium chloride but not to norepinephrine, phenylephrine, histamine or carbamylcholine. In contrast, rabbit and guinea-pig jugular veins contracted to norepinephrine, phenylephrine and histamine, although contractions to norepinephrine were small in guinea-pig jugular veins. Norepinephrine, phenylephrine and histamine produced a concentration-dependent sustained relaxation of serotonin-induced contractions in the rat jugular vein, as did isoproterenol, nitroglycerin and papaverine. Propranolol blocked relaxation to norepinephrine, phenylephrine and isoproterenol whereas metiamide, a H2 receptor antagonist blocked relaxation to histamine. alpha adrenergic receptor blockade with phentolamine or prazosin resulted in greater relaxation to norepinephrine whereas cocaine did not enhance norepinephrine-induced vasodilation. This study supports the premise that norepinephrine may exert prominent beta adrenergic receptor stimulation in some blood vessels and that this effect may be more apparent in veins than arteries.

Neuronal uptake inhibitors, nisoxetine and fluoxetine on rat vascular contractions.

The importance of neuronal uptake processes in rat arteries and veins was compared using nisoxetine and fluoxetine, selective inhibitors for neuronal uptake of norepinephrine and serotonin, respectively. Nisoxetine (10(-7) - 10(-5) M) increased the sensitivity to exogenous norepinephrine in the portal and mesenteric veins (10-fold) and in the mesenteric artery (2.5-fold). Responses to field stimulation were also increased afternisoxetine in all three vessels. After nisoxetine, aortic responses to norepinephrine were unaltered and in all tissues, serotonin-induced contractions were reduced. Fluoxetine did not potentiate responses to norepinephrine or to field stimulation except in the mesenteric vein where sensitivity to norepinephrine was increased and the relaxation rate after field stimulation was prolonged. Although serotonin has been detected in blood vessels, fluoxetine did not increase vascular responses to serotonin. These studies suggest that rat mesenteric veins have a highly sensitive neuronal uptake mechanism of norepinephrine. Furthermore, these data provide indirect evidence against a functionally important serotonergic uptake process in rat blood vessels and suggest that neuronal uptake of serotonin does not exert a major role in terminating the vascular action of this biogenic amine.

Specific enhancement of norepinephrine-induced contraction in rat veins after beta adrenergic antagonists.

Propranolol markedly increased the norepinephrine-induced maximal force in circular smooth muscle of the rat portal, mesenteric, renal and, to a lesser extent, femoral veins without affecting aortic or mesenteric artery responses to norepinephrine. Furthermore, two other beta receptor antagonists, practolol and N-isopropylmethoxamine, specifically enhanced maximal venous responses to norepinephrine. Contractions to norepinephrine, but not to serotonin, were increased by propranolol only in veins, even after the vasodilator, papaverine. The ability of propranolol to enhance norepinephrine-induced contraction in these rat veins paralleled the effectiveness of isoproterenol to relax such tissues. In addition, beta receptor antagonists enhanced the response of veins to the field stimulated release of norepinephrine from sympathetic nerves. These data support the conclusion that beta adrenergic stimulation modulates norepinephrine-induced constriction in certain rat veins but not in the aorta or mesenteric artery.

Comparison of arteries with longitudinal and circular venous muscle from the rat.

Rat portal, mesenteric, renal, and femoral veins possess functionally responsive circular and longitudinal smooth muscle layers in vitro. In contrast to the dominant rhythmically active longitudinal muscle of portal veins, rat longitudinal mesenteric veins lacked rhythmic activity and developed maximal force equivalent to that of mesenteric circular muscle. Renal and femoral veins exhibited predominantly circular smooth muscle responses. Rat veins must be subjected to between 1 g (renal and femoral) and 4 g (circular portal and mesenteric) of passive forse for optimal responsiveness. Contractile response to vasoactive agent including carbamylcholine, serotonin, and norepinephrine was quantitatively different among veins. Femoral veins developed greater maximal force in response to norepinephrine than to KCL, and the responses to norepinephrine were not altered by cocaine. In contrast, cocaine markedly potentiated responses to norepinephrine in portal, mesenteric, and renal veins and, to a lesser extent, in the mesenteric artery. These data demonstrate heterogeneity in rat venous tissue and suggest that neuronal innervation may markedly influence responses to norepinephrine in some, but not all, rat blood vessels.